1. Field of the Invention
The present invention relates to a damper, accommodated in a liquid jetting apparatus such as an ink-jet printer, which has a reservoir storing a liquid for relaxing pressure fluctuation of a liquid; a head unit which includes the damper; a liquid jetting apparatus; and a method of discharging air from the reservoir of the damper.
2. Description of the Related Art
An ink jet-printer, as an example of a liquid jetting apparatus, mainly includes a liquid supply unit having: a jetting head in which nozzles are formed; a damper which is connected to the jetting head, which stores a small amount of ink and which absorbs a pressure fluctuation of ink; and a casing which accommodates the jetting head and the damper. This liquid supply unit is arranged to face a transported recording paper, and forms an image on the recording paper by jetting an ink from the nozzles while reciprocating in a direction orthogonal to a transporting direction of the recording paper. Moreover, in such a printer, an ink cartridge of a large capacity which is independent of the liquid supply unit is provided to a body thereof, and the ink cartridge and the damper are connected by a flexible tube. Thus a so-called tube-supply type printer has hitherto been known. Then, a small sizing of the liquid supply unit has been facilitated while increasing an amount of the ink supplied.
In a known printer, four ink reservoirs corresponding to inks of four colors namely, black, cyan, magenta, and yellow are provided in the damper. Each of the ink reservoirs has a thin and flat shape, and the ink reservoirs are stacked in a vertical direction to overlap in a plan view. Moreover, one of an upper portion and a lower portion of each ink reservoir is demarcated by a resin member, and the other one is demarcated by a flexible film. Consequently, a pressure wave generated in the ink is relaxed or absorbed by a deformation of this flexible film, and an ink jetting performance (jetting capability) is stabilized.
It has been known that air grows in a channel which guides the ink from the ink cartridge to the jetting bead when the printer is not used so frequently. When this air enters the jetting head, there is a possibility that a desired jetting performance cannot be achieved. Whereas, when an air storage space having a predetermined capacity for trapping the air is provided, it is possible to prevent an entry of air into the jetting head. However, when this space is made to have a large capacity in order to trap a large amount of air, it becomes difficult to reduce the size of the liquid supply unit. Therefore, in the printer as described above, an ink outflow channel which is elongated in a vertical direction is formed at half way from the ink reservoir to the jetting head, and an opening (upper-opening) is formed in an upper-portion thereof and is covered by a gas-liquid separation membrane. Accordingly, the air is discharged to outside of the ink outflow channel through the gas-liquid separation membrane.